Prior art of possible relevance includes the following U.S. Letters Pat. No.: 3,894,580 issued July 15, 1975 to Chartet; U.S. Pat. No. 4,324,028 issued Apr. 13, 1982 to Severson; U.S. Pat. No. 4,324,290 issued Apr. 13, 1982 to Moranne; U.S. Pat. No. 4,331,201 issued May 25, 1982 to Hesse; and U.S. Pat. No. 4,448,321 issued May 15, 1984 to Hanlet. Of the foregoing, the Hesse and Moranne patents have the most relevance.
The effort by the automotive industry to reduce the weight of vehicles to thereby improve mileage is seen in increasing use of non-metallic materials is various parts of vehicles. Heat exchangers, more commonly termed radiators, are no exception. While metal materials are still employed in the cores of such heat exchangers because of their greater thermal conductivity over other materials, other heat exchanger components that do not require good thermal conductivity are being made of plastic. A primary example is the so-called tanks which are fitted to the heat exchanger core most typically by securement to the header plates which define the ends of such cores.
Because the joint between the header plate and the tank is one of dissimilar materials, prior techniques of brazing or soldering the joints can no longer be employed. In lieu thereof, to effect the necessary seal, a gasket is disposed between the tank and the header plate and any of a variety of means are employed to hold the components in assembled relation with the gasket under compression to assure a seal at the operating pressure for which the heat exchanger was designed.
It is, of course, necessary that the means employed to effect the connection be strong and long lived to prevent leakage. At the same time, it is desirable that the means be such that disassembly of the component parts can be effected when required for serving. It is also desirable that the means utilized lend themselves to use in mass production to minimize cost.
Attempts to achieve these objects have resulted in proposals wherein a header plate is provided with a peripheral groove in which the gasket to be compressed may be disposed. The tank is provided with a peripheral flange sized to be wholly received in the groove and adapted to compress the gasket therein. The outer wall of the groove is then deformed in part to overlie the flange and the tank and hold the same in a position compressing the gasket. This approach is exemplified by the above identified Morrane and Hesse patents.
Unfortunately, because this approach involves deformation of a metal wall which necessarily may be sufficiently thin so as to be easily deformed, the same may not always be as strong as might be desired. Pressure within the system during operation will act against the deformed material and tend to deform it back toward the original configuration. When such occurs, the compressive forces exerted on the gasket are lessened and leakage may occur.
Moreover, these constructions require a relatively wide groove or recess to receive the entirety of the width of the flange. This results in a relatively long moment arm between the point of deformation of the outer groove wall over the flange and the point whereat the inner groove wall meets the header plate which increases the force concentration at the latter location.
Furthermore, the sealing methods employed in such constructions are totally dependent upon the degree of compressive force maintained on the seal by the tank-header plate connection. Consequently, lessening of this force lowers the efficiency of the seal.
In addition, because these constructions require deformation of the flange after the tank is assembled thereto, the assembly process is undesirably expensive in view of the need for fixtures and specialized tooling to provide deformation of the flange.
The present invention is directed to overcoming one or more of the above problems.